I'll get a small pension, and the way I am valuing it is:

[Pension in today's $]*25* 1.04^-[number of years till I can draw the pension]

So, for example I am 45 and can get my pension at 55. It is worth $13,000 a year in today's dollars and is indexed to CPI. It will pay until I die. So I value it as

$13,000*25*(1.04)^-10 = $219,500.

I feel that this method is consistent with the 4% rule.

Each year the future payout gets inflated by CPI and the discount gets reduced when I value my stash. So let's say this year we have 3% inflation, then my pension increases to $13,390 and I would value the pension as

$13,390*25*1.04^-9 = $235,190.

Once I get to 55 I won't value it this way. I'll just reduce the spending I am trying to cover by the pension I have, just like my house (ie: I don't include the house and I don't include rent expense).

But for now, I like to include the pension in my stash calculations as it just makes for simple comparisons with my expenditure budget, and required withdrawal rate, particularly as I won't get the pension for 10 years, so it's value needs to be discounted.